As a general set-up, that +120 to +270 period is classic snow potential for MBY... if we were 4-5 weeks further on in the season. Graupel city!

That +300 chart is tantalising on first view, isn't it? That energy was beginning to slide under from +294 and you're willing it to continue and for the low to follow it. Then high pressure ridges up from Africa and it's goodnight, Vienna.

If they are using the now defunct stations data to compare current data with, that cannot be acceptable. The differences between even two closeby stations can be pretty significant. One will not capture the hyperlocal nuances of the other. It isn't possible. 

That's using the tried and tested old Meteociel charts:

https://www.meteociel.fr/cartes_obs/gens_display.php?x=&y=&run=12&ville=Londres&lat=51.5085&lon=-0.12574&runpara=0&type=6&ext=0 

Okay, there are now 30 members (plus the op and control), so not as impressive as it used to be, but even so - it's enough to slightly raise an eyebrow.

The other interesting thing is the rapid cyclogenesis that's possible in the 144-168 timeframe, as shown on the MetO and GEM output. Even though 850s don't seem remarkable, it's the sort of thing that can cause unexpected snowfall to pop up in places on the west and NW side of the low as it pulls away.

At least there's more excitement in the models now than there has been over the past few weeks! 😁

Still a little off an ensemble watch for -10’s !

Indeed! There are a few other things I'd need to see before one of those - ice days as a possibility on the ECM ensembles, for example, as well as -10s showing up on the ECM plumes.

https://charts.ecmwf.int/products/opencharts_meteogram?base_time=202411110000&epsgram=classical_15d&lat=51.4333&lon=-1.0&station_name=Reading 

Some of the GEFS members keep the generally cold pattern going for quite some time, and there's at least one with widespread snow moving south across the UK.

One member go down as low as -15C over Nuneaton ensembles while the main line is -6C on 18th November which now ear marked for the coldest air to hit here.  At least some interest about possible out of blue snowfall but mostly happy to see lot of sunshine with it.

Enjoy, as we normally spend all winter looking for these kind of charts ( even at +168!)

“Temperatures falling below average and feeling particularly cold in the strong winds”

…along with “significantly colder” as the opening line 

Wouldn't be suprised to see the SE get a little channel disturbance of this...Tunbridge Wells in firing line again like Dec 2022...

Out of interest, is that snow field actual modelled snow, or is it still the old "one flake of sleet in amongst the rain" field? If GFS now has sleet (rain/snow mixed) and pure snow, would it be possible to have the colours changed? Maybe pink as-is for sleet and white/grey for snow?

As for the GFS run, it has 70+ mph gusts here as that low pulls away - with snow over the Downs. Here it'd just be utterly miserable!

It shows the potential of rapid cyclogenesis, though, something which is being flagged up repeatedly of late.

If I had to put money on it, I'd suggest we're likely to see at least one low zipping across or close to the SE, with lots of cold rain and strong winds down here and some snow mostly over higher ground further north and west, perhaps the odd bit making it down to lower levels in e.g. the Midlands and areas west of say Reading.

Definitely something to keep an eye on, anyway.

If pieces fall together there is a raised chance of a significant event as per GfS 00Z run.

GFS Op - HP hangs on over or just W of Britain to Fri 15th, but by Sunday the large LP over Scandinavia is projecting N-lies across Britain, and this N-ly stream spawns a set of cold and stormy LPs running from the W or SW; Mon 18th 980mb N Sea, Tue 19th 975 mb S Ireland (this rapidly traverses England), Thu 21st 965mb Devon running up the Channel. There is then a shift as Atlantic rather than Scandinavian LP controls British weather; trough 995mb Brittany Sun 24th runs up the west coast followed by another Tue 26th closer in before HP begins to reassert itself 1040b Biscay Thu 28th. 

BBC (Meteo Group) weather shows the breakdown at the end of this week as a flabbier affair; cold from the north, certainly, but spread over a larger area without the storms offered by GFS.

ECM - agrees with GFS to Mon 18th but the LP by then in the N Sea 990mb stays around S Norway and contents itself with extending troughs to Ireland 1005mb Wed 20th, N France 995mb Thu 21st and back to W Scotland 1000mb Fri 22nd. Still definitely cold but not nearly as stormy.

GEM - favours the cold and stormy outlook after Mon 18th ; 970 mb Devon Wed 20th moving rapidly to N Sea dragging a second local LP 990mb W Scotland behind it

GEFS - a big dip in temp to 6 or 7 C below by Mon 18th, colder than shown yesterday and with better (though not perfect) ens agreement. Temps stay low for a week, op and control amongst the lowest, enough milder runs to drag the mean back to norm by Sun 25th while op & control stay on the cold side. Rain starts 17th Nov, heavy and persistent in the S, moderate amounts for Scotland and the N. Snow row figures widely in the 20s for Scotland, even a few reaching 5 or 6/33 on the south coast, so snow likely on high ground anywhere.

Who fancies widespread deep snow next Monday followed by several widespread ice days?

If you do, PTB26 has what you want...

https://www.meteociel.fr/modeles/gefs_cartes.php?code=26&ech=144&mode=0&carte=0&ext=0 

Of course it's a humongous outlier, one of the biggest I've ever seen - but the fact that it's at only 144 shows what happens if you roll five sixes....

EDIT: The funny thing is synoptically it's actually rather similar to many of the other runs / members, it just runs the trigger low further south. It shows what can happen if you get snow on the ground, it seems GEFS now has enough layers to model the effects of a cold boundary layer well. (We all know, for example, that once you have snow on the ground you no longer need to look for such low 850s / thicknesses for further snow).

One thing's for sure - we've now more excitement to look forward to than in the previous few months combined! Silly season is upon us, folks, buckle up and enjoy the ride! 😁

1) It hasn't changed

2) It is a categorical variable, so it doesn't provide the amount

I've taken a look through the variables available and there isn't anything to replace it that I can see. Therefore, I think you'll basically find it to be the same wherever you view GFS precipitation type forecast charts.

Personally, I always take a look at the accompanying snow depth charts from the GFS  / GEFS, because they can ameliorate the issue to a degree. So you get something like this:

From GEFS 00Z you get this for Berkhamsted:

Both of the above are generated using snow depth variables in the data sets rather than being derived from them. That said, IMO the GFS / GEFS badly overestimate snow depths, at least for the UK. I'm not sure if that's because they over forecast the amount of precipitation or if other factors such as compression and melting in marginal conditions are the main issue. There is a variable which gives the total amount of water that would be produced if all the accumulated snow on the ground were melted that could help with that, but I don't have the time to delve into it.  

Thank you for the detailed info! 👍

It's disappointing in a way that GFS doesn't provide finer differentiation of rain, rain/snow mixed and pure snow, but it's not too surprising - that, along with the snow depth overestimation, stems (IMO) from a model designed mainly for the continental climate which North America enjoys. They seem to have less (British style) sleet out there, and I guess that more often than not when the "snow" element is triggered it'll be snow rather than sleety, slushy stuff.

The Canadian GEM suffers in a similar way with its snow depth estimations too. I suspect in both cases they're assuming dry powder snow ratios (again, reasonable considering that'll be the main type of snow out there) rather than the sopping wet slushy stuff we tend to get.

All in all it just means we'll have to continue taking GFS' snow charts with a very large dose of salt!

Would be nice for us here with lot of snow and at least something interesting and more sunshine in between and glad no HP over us next week, don't want any HP anymore after the recent HP brought 2 weeks of gloom.  Still some HP again this week but not over us more to the west so keep gloom out.

https://www.meteociel.fr/modeles/gefs_cartes.php?code=1&ech=168&mode=0&carte=0&ext=0